In general floor planks should be installed perpendicular to the ceiling joists although the presence of a plywood sub ceiling or a layer of perpendicular furring strips will allow you to install parallel to the joists.
Decorative wood between floor joists ceiling.
Owt ornamental wood ties ironwood 6 in.
Attic and floor dead load of 10 psf.
You may need to lift insulation or plywood to see the joists.
Floor covering is the aptest description since everything below the substrate can be considered the real floor in terms of structure and permanence.
Unless you have a finished attic the ceiling joists are typically exposed.
Ceiling board allows you to heat your room far more efficiently.
Bonus room floor joist selection guide.
Floor live load of 40 psf between the kneewalls.
Generally floor or ceiling joists run parallel to the rafters.
Lower ceilings shrink the volume of the room to be heated.
For finished ceilings first disconnect the electricity and remove all light fixtures and other obstacles.
Straight gable roof framing is assumed for selection table.
You would be able to check if this is the case in your home by going up into the attic.
Ceiling drywall hides the unpainted unfinished wood of joists beams or the floorboards supported by the beams plus a lot of other junk detailed below.
Floor joists and ceiling joists serve similar purposes.